Stormwater Sampling Tips & Rainy Season Prep

As the California rainy season approaches, sampling for industrial impacts on storm water discharge will be underway. California's Industrial General Permit (IGP) presents covered facilities with many regulatory responsibilities. Having a comprehensive understanding of sampling requirements along with strategies on how to capture the best sample ensures sampling results that best represent your facility's operations and impacts to storm water. 

California Stormwater Sampling Requirements

When it comes to sampling, there are basic requirements which need to be met to ensure regulatory compliance.

Samples must be collected within four (4) hours of the time when storm water discharge begins, or within four (4) hours of the start of facility operations if the Qualified Storm Event (QSE) occurs within a 12-hour period. A facility covered under the IGP must sample two (2) QSEs from each half of the reporting year, from July 1st - December 31st, and January 1st-June 30th.


Once a sample has been sent to a lab for analysis and the results are returned to your facility, the analytical results must be uploaded to California's electronic reporting system, Stormwater Multiple Application and Report Tracking System (SMARTS,) in the form of an Ad Hoc Report. The deadline to submit an Ad Hoc Report is 30 days from the date you receive the laboratory report. It is important to note that all Ad Hoc Reports can be publicly viewed on SMARTS and are frequently monitored by third parties. Ensuring data are uploaded accurately and on time is crucial to protecting your facility from unwanted legal attention.

What should California facilities do to prepare for the first QSE of the rainy season?

Once you have chosen sampling locations that best represent your industrial operations, it is time to prepare for QSEs.

August/September is an excellent time to prepare, as the rainy season in California typically begins around October. Upon receiving your sampling kits, ensure all bottles, solutions, and containers are correct and not expired. The first QSE of the season is a very important event, as it can potentially yield unrepresentative sampling results due to a buildup of dust from aerial deposition. The recent wildfires will contribute to this phenomenon, making proper preparation all the more important. Unrepresentative sampling results from the first QSE of the rainy season can trigger unnecessary and expensive monitoring and compliance requirements for your facility, as well as potentially triggering a more intensive level status under the IGP.

KERAMIDA highly recommends that facilities do the following:

  • Deep clean all outdoor areas which may be exposed to storm water - collect and dispose of runoff if using water to clean said areas.

  • Sweep all rooftops.

  • Clean out catch basins.

  • Replace catch basin inserts and filters, if needed.

  • Perform maintenance on storm water treatment units.

  • Check swales and ditches for trash and debris.

  • Ensure all Best Management Practices (BMPs) are in place and implemented before sampling your first QSE.

  • Weather channels can be monitored to help predict when a QSE may occur.

  • Ensure your sampling locations are kept clean. Litter and debris can impact your sampling results, potentially resulting in data unrepresentative of your compliance efforts.

  • Have all of your sampling accessories prepared and easily accessible, including but not limited to: sampling kit(s), rubber boots, gloves, buckets, thief.

  • Note that pH must be analyzed within 15 minutes of sample collection. As a reminder, if your facility is in Level 1 or 2 for pH, a pH probe is required to test for pH during a QSE.

It is important to regularly observe your stormwater sampling locations during all rain events, including non-QSE’s.

Note how the water looks:

  • Is it murky?

  • Is there a noticeable odor?

  • Are there floating or suspended solids?

  • Is there an oil sheen or foam?

  • Are your BMPs working?

Record any and all abnormalities with your sample or sampling locations:

  • Maintain a rain log with all important storm water documents. Maintaining a rain log is an excellent way to ensure that your facility is less liable for unrepresentative sampling results.

  • KERAMIDA recommends taking pictures of any abnormalities and keeping them with your storm water records.

Stormwater sampling for facilities near California’s wildfires:

If your facility is in an area that has been impacted by one of California’s many wildfires, we do not recommend sampling the first QSE of the season.


The sample would be potentially impacted by ash and aerial deposition, including fire retardant chemicals which contain aluminum, present on all outside areas of your facility which could be exposed to stormwater, especially on all roofs. Many facilities have already had their sampling results impacted by wildfire activities, and this presents an entirely new compliance effort.

If you do choose to sample the first QSE, we recommend doing the following:

  • Deep cleaning all outdoor areas which could be exposed to storm water

  • Deep cleaning and thoroughly sweeping all roofs

The Waterboard is aware that sampling results could potentially be impacted from the wildfires, but it is unclear to what degree they will take this into consideration.

Stormwater Sampling Tips

Sampling DO’s:

Stormwater Sampling Do’s

Stormwater Sampling Do’s

  • Do use the right equipment. Use the correct designated bottle for each parameter provided in your sampling kit. Keep all equipment clean.

  • Do wait at least twenty (20) minutes after the QSE starts before sampling. This allows the initial flush of pollutants to be cleared from the discharge point.

  • Do wear protective gear when sampling. Gloves should be changed before sampling each location point.

  • Do sample each location that is designated on your Storm Water Pollution Prevention Plan (SWPPP).

  • Do sample flowing or cascading water. If water is moving quickly or pipes are filling with flowing water, target the mid-line of the discharge stream.

  • Do fill out the Form 2 - Stormwater Sampling Event Visual Observation - for each QSE you sample. Keep completed forms with all storm water records.

Sampling DON’Ts:

stormwater Sampling Don’ts

stormwater Sampling Don’ts

  • Do not allow gravel and debris to enter your sample bottle. The bottle opening should rest gently on the surface of flowing water.

  • Do not drag the bottle along the bottom of the discharge point. Doing so could increase the amount of sediment in your sample.

  • Do not sample upstream of your BMPs, only sample downstream of BMPs. You want your hard work to be represented in the sampling results!

  • Do not sample still, stagnant, or non-flowing water.

  • Do not allow storm water to cross a large paved, non-industrial area before sampling. This only increases the opportunity for debris and particulate matter to impact the sample.

  • Do not allow a lack of training or personnel turnover to be a reason for not sampling all of your facilities’ required parameters. Third parties and the Waterboard do not look favorably upon this reasoning if the four (4) required QSEs are not sampled and submitted to SMARTS.

KERAMIDA’s QISP-certified California stormwater consultants can work with you to choose sampling location(s) that best represent your facility’s industrial operations, including re-evaluating those locations regularly as your industrial operations expand or change. For assistance with stormwater inspections, management, IGP compliance, and industrial stormwater permitting, contact us or call KERAMIDA today at (800) 508-8034 to speak directly with a stormwater compliance consultant. 

Blog Author


Jodie Crandell, QISP, QEP, TOR
Senior Project Manager

Contact Jodie at